Artificial jellyfish 'Medusoid' swims in a heartbeat: Creation is an amalgam of silicone polymer and heart muscle cells

July 22, 2012

This is a still of the artificial jellyfish. Credit: Harvard University and Caltech

Using recent advances in marine biomechanics, materials science, and tissue engineering, a team of researchers at Harvard University and the California Institute of Technology (Caltech) have turned inanimate silicone and living cardiac muscle cells into a freely swimming "jellyfish."

The finding serves as a proof of concept for reverse engineering a variety of muscular organs and simple life forms. It also suggests a broader definition of what counts as synthetic life in an emerging field that has primarily focused on replicating life's building blocks.

The researchers' method for building the tissue-engineered jellyfish, dubbed "Medusoid," was published in a Nature Biotechnology paper on July 22.

An expert in cell- and tissue-powered actuators, coauthor Kevin Kit Parker has previously demonstrated bioengineered constructs that can grip, pump, and even walk. The inspiration to raise the bar and mimic a jellyfish came out of his own frustration with the state of the cardiac field.

Similar to the way a human heart moves blood throughout the body, jellyfish propel themselves through the water by pumping. In figuring out how to take apart and then rebuild the primary motor function of a jellyfish, the aim was to gain new insights into how such pumps really worked.

"It occurred to me in 2007 that we might have failed to understand the fundamental laws of muscular pumps," says Parker, Tarr Family Professor of Bioengineering and Applied Physics at the Harvard School of Engineering and Applied Sciences (SEAS) and a Core Faculty Member at the Wyss Institute for Biologically Inspired Engineering at Harvard. "I started looking at marine organisms that pump to survive. Then I saw a jellyfish at the New England Aquarium and I immediately noted both similarities and differences between how the jellyfish and the human heart pump."

To build the Medusoid, Parker collaborated with Janna Nawroth, a doctoral student in biology at Caltech and lead author of the study, who performed the work as a visiting researcher in Parker's lab. They also worked with Nawroth's adviser, John Dabiri, a professor of aeronautics and bioengineering at Caltech, who is an expert in biological propulsion.

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This movie demonstrates jellyfish-like body contraction and free-swimming of optimally designed Medusoid constructs. Medusoids were paced at 1 Hz through an externally appliedmonophasic square pulse (2.5V/cm, 10ms duration). The first scene shows a mature constructstill attached at its center to its casting mold, just prior to release. (Note that the striatedappearance of the casting mold is caused by its fabrication process; in particular, this striationdoes not reflect the alignment of the muscle tissue on top of the silicone membrane covering themold). Subsequent scenes show exemplary propulsion of free-swimming Medusoids. Video: Nature Biotechnology.

"A big goal of our study was to advance tissue engineering," says Nawroth. "In many ways, it is still a very qualitative art, with people trying to copy a tissue or organ just based on what they think is important or what they see as the major componentswithout necessarily understanding if those components are relevant to the desired function or without analyzing first how different materials could be used."

It turned out that jellyfish, believed to be the oldest multi-organ animals in the world, were an ideal subject, as they use muscles to pump their way through water, and their basic morphology is similar to that of a beating human heart.

A still of the artificial jellyfish "swimming" in container of ocean-like salt water. Note: the color and contrast of the artificial jellyfish has been digitally enhanced to make it easier to view. Image courtesy of Harvard University and Caltech.

To reverse engineer a medusa jellyfish, the investigators used analysis tools borrowed from the fields of law enforcement biometrics and crystallography to make maps of the alignment of subcellular protein networks within all of the muscle cells within the animal. They then conducted studies to understand the electrophysiological triggering of jellyfish propulsion and the biomechanics of the propulsive stroke itself.

Based on such understanding, it turned out that a sheet of cultured rat heart muscle tissue that would contract when electrically stimulated in a liquid environment was the perfect raw material to create an ersatz jellyfish. The team then incorporated a silicone polymer that fashions the body of the artificial creature into a thin membrane that resembles a small jellyfish, with eight arm-like appendages.

Using the same analysis tools, the investigators were able to quantitatively match the subcellular, cellular, and supracellular architecture of the jellyfish musculature with the rat heart muscle cells.

The artificial construct was placed in container of ocean-like salt water and shocked into swimming with synchronized muscle contractions that mimic those of real jellyfish. (In fact, the muscle cells started to contract a bit on their own even before the electrical current was applied.)

"I was surprised that with relatively few componentsa silicone base and cells that we arrangedwe were able to reproduce some pretty complex swimming and feeding behaviors that you see in biological jellyfish," says Dabiri.

Their design strategy, they say, will be broadly applicable to the reverse engineering of muscular organs in humans.

"As engineers, we are very comfortable with building things out of steel, copper, concrete," says Parker. "I think of cells as another kind of building substrate, but we need rigorous quantitative design specs to move tissue engineering to a reproducible type of engineering. The jellyfish provides a design algorithm for reverse engineering an organ's function and developing quantitative design and performance specifications. We can complete the full exercise of the engineer's design process: design, build, and test."

In addition to advancing the field of tissue engineering, Parker adds that he took on the challenge of building a creature to challenge the traditional view of synthetic biology which is "focused on genetic manipulations of cells." Instead of building just a cell, he sought to "build a beast."

Looking forward, the researchers aim to further evolve the artificial jellyfish, allowing it to turn and move in a particular direction, and even incorporating a simple "brain" so it can respond to its environment and replicate more advanced behaviors like heading toward a light source and seeking energy or food.

Along with Parker, Nawroth, and Dabiri, contributors to the study included Hyungsuk Lee, Adam W. Feinberg, Crystal M. Ripplinger, Megan L. McCain, and Anna Grosberg, all at Harvard.

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"I was surprised that with relatively few componentsa silicone base and cells that we arrangedwe were able to reproduce some pretty complex swimming and feeding behaviors that you see in biological jellyfish," says Dabiri.

how does this help anyone suffering an ailment have a better life? all they're really doing is saying "we think we can create life just like god created us." man's own arrogance is the direct cause of his downfall right around the corner, within years.

Anyone who has seen the movie 'Die Hard' with Bruce Willis will understand the basic concept here. In Die Hard, by applying a voltage to a dead terrorist, John McClain was able to stimulate a gripping motion in the cadaver, which forced it to fire an automatic weapon that it was holding. Similarly, the heart cells within the Medusoid contract when a voltage is applied.

I like Nature's version better. It seems to function more smoothly and more efficiently.

It's more complex and doesn't waste as much energy on the back strokes.

Still serious congratulations are in order to the artificial team. I hadn't considered such amalgams of living tissue and structural silicone was possible.

This is all well known conceptually in the fields of research into medical nanotechnology.

There is no good reason you couldn't create micro-channels in the silicon and run nerve, muscle, and blood vessels through the channels, producing efficient pumping action as well as self-feeding and self-healing of the biological materials.

For medical purposes, I suppose implants will need to be specially crafted from muscle tissue samples from the patient or from compatible donors, although they may be aiming for a 100% synthetic, yet life-like pump, which would be more ideal for mass production and in prosthetics and artificial organs.

If you can create artificial organs that feed on glucose and oxygen, just like our own organs, and handle their own waste disposal, then you don't need to be bothered with donors or rejection complications, and you don't even need batteries...

But in order to do that, you have to start somewhere by understanding how and why natural organs work the way they do.

"I was surprised that with relatively few componentsa silicone base and cells that we arrangedwe were able to reproduce some pretty complex swimming and feeding behaviors that you see in biological jellyfish," says Dabiri.

I like Nature's version better. It seems to function more smoothly and more efficiently.

Still serious congratulations are in order to the artificial team. I hadn't considered such amalgams of living tissue and structural silicone was possible.

Wha!?! You never looked at yourself in a mirror, you - mean, evil, world-conquest-Dr.Evil-Decarian-kind of guy, you! Hey! We got a sale on at the store. Big discount on old Apple 'Air' laptops and 60% off a selection of games when you buy one....Dude!!! word-to-ya-muthasword-

I hadn't considered such amalgams of living tissue and structural silicone was possible.

Indeed, it is very impressive. Much more important than the attention it got. Historicaly important if I may be so bold, even with their limitations that they so well describe. But then, there are some many important developments every day.

But I am surprised that no one mentioned yet the term cyborg: a cybernetic organism, intended to describe exactly this co-existence of biological and mechanical parts. This one is more advanced than a person wearing glasses.-.

In Die Hard, by applying a voltage to a dead terrorist, John McClain was able to stimulate a gripping motion in the cadaver, which forced it to fire an automatic weapon that it was holding

There is an example that it might be better than a cinema scene: it was known since the early days of electricity --one and a half century before-- that you can take the legs of frog, apply electricity on the muscle and make them move.

Why it took so long to come to this Medusoid?-.

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